The disclosure of Japanese Patent Application No. 2001-133221 filed on Apr. 27, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a warm-up control apparatus and a warm-up control method for an internal combustion engine. More particularly, the invention relates to a warm-up control apparatus which is installed in a vehicle equipped with a brake booster that uses negative pressure in an intake pipe of an internal combustion engine and which performs a warm-up control of the engine by retarding the ignition timing and increasing the amount of intake air, and to a warm-up control method.
2. Description of the Related Art
Internal combustion engines adopt an ignition timing retarding control for improving a warm-up characteristic of a catalyst provided in an engine exhaust system. This control is based on a fact that if the ignition timing is retarded, the combustion end timing is retarded and the combustion speed reduces, so that the exhaust heat loss increases and a high-temperature exhaust gas is supplied to the catalyst, and therefore early warm-up of the catalyst can be achieved. Retardation of the ignition timing involves a reduction in engine torque. Therefore, in general, when the ignition timing retarding control is executed, a control of increasing the amount of intake air is simultaneously executed in order to prevent reduction of engine torque (see, for example, Japanese Patent Application Laid-Open Nos. 5-26138 and 11-93813, etc.).
Brake boosters are widely employed in vehicles in order to reduce the brake pedal operating force at the time of a braking operation. A typical brake booster uses the intake negative pressure of the engine as a boost power source. During execution of the warm-up control involving an increase in the amount of intake air and a retardation of the ignition timing, the intake pipe negative pressure tends to become low or insufficient, and therefore the brake performance reduces. Therefore, during execution of the warm-up control, an unpleasant braking feel may result when the brake is operated.
Accordingly, it is an object of the invention to provide a warm-up control apparatus and a warm-up control method for an internal combustion engine that are able to secure a good braking performance by restraining a warm-up control at the time of a braking operation during execution of the warm-up control.
In order to achieve the aforementioned object, a first aspect of the invention provides a warm-up control apparatus of an internal combustion engine and a warm-up control method, in which a brake booster that uses a negative pressure in an intake pipe of the internal combustion engine is provided, and a warm-up control of the internal combustion engine is performed by retarding an ignition timing and increasing an amount of intake air. The amount of intake air set in relation to the warm-up control is reduced if a brake pedal is operated during execution of the warm-up control.
In the warm-up control apparatus and the warm-up control method in the first aspect of the invention, the amount of intake air increased by the warm-up control is reduced simultaneously with detection of an operation of the brake pedal, so that the intake pipe negative pressure will be recovered. Therefore, although there is a slight delay in timing, the negative pressure for use by the brake booster is secured, and reduction in the brake performance can be curbed.
In a warm-up control apparatus and a warm-up control method of an internal combustion engine in accordance with a second aspect of the invention, a brake booster that uses a negative pressure in an intake pipe of the internal combustion engine is provided, and a warm-up control of the internal combustion engine is performed by retarding an ignition timing and increasing an amount of intake air. In the warm-up control apparatus and the warm-up control method, the amount of intake air set in relation to the warm-up control is reduced if an accelerator is off while a vehicle is running at or above a predetermined vehicle speed during execution of the warm-up control.
If the accelerator is off while the vehicle is running at or above a predetermined vehicle speed, there is a possibility of operation of the brake. In the second aspect, therefore, the amount of intake air increased by the warm-up control is reduced simultaneously with detection of the accelerator-off state, so that the intake pipe negative pressure will be recovered at an earlier timing. Therefore, a good braking performance is secured, and good preparation for a braking operation is made.
In a warm-up control apparatus and a warm-up control method of an internal combustion engine in accordance with a third aspect of the invention, a brake booster that uses a negative pressure in an intake pipe of the internal combustion engine is provided, and a warm-up control of the internal combustion engine is performed by retarding an ignition timing and increasing an amount of intake air. In the warm-up control apparatus and the warm-up control method, the amount of intake air set in relation to the warm-up control is reduced if a decreasing rate of an amount of accelerator operation is greater than or equal to a predetermined value while a vehicle is running at or above a predetermined vehicle speed during execution of the warm-up control.
If the decreasing rate of the amount of accelerator operation is greater than or equal to a predetermined value while the vehicle is running at or above a predetermined vehicle speed, there is a high probability of operation of the brake. In the third aspect, therefore, the amount of intake air increased by the warm-up control is reduced simultaneously with detection of such a reduction in the amount of accelerator operation, so that the intake pipe negative pressure will be recovered at a further earlier timing. Therefore, a good braking performance is secured, and good preparation for a braking operation is made.
In a warm-up control apparatus and a warm-up control method of an internal combustion engine in accordance with a fourth aspect of the invention, a brake booster that uses a negative pressure in an intake pipe of the internal combustion engine is provided, and a warm-up control of the internal combustion engine is performed by retarding an ignition timing and increasing an amount of intake air. In the warm-up control apparatus and the warm-up control method, the amount of intake air set in relation to the warm-up control is reduced if an increasing rate of a degree of throttle opening is greater than or equal to a predetermined value during execution of the warm-up control.
If the increasing rate of the degree of throttle opening is greater than or equal to a predetermined value, the warm-up is rapidly accelerated, so that there is a danger of overheat of the catalyst and restraint of the warm-up control will not cause a problem. In this aspect, the amount of intake air increased by the warm-up control is reduced simultaneously with detection of such an increase in the degree of throttle opening, so that the intake pipe negative pressure will be recovered. Therefore, a good braking performance is ensured beforehand, and good preparation for a braking operation is made.
In a warm-up control apparatus and a warm-up control method of an internal combustion engine in accordance with a fifth aspect of the invention, a brake booster that uses a negative pressure in an intake pipe of the internal combustion engine is provided, and a warm-up control of the internal combustion engine is performed by retarding an ignition timing and increasing an amount of intake air introduced into the engine via the intake pipe. In the warm-up control apparatus and the warm-up control method, the amount of intake air set in relation to the warm-up control is reduced if during execution of the warm-up control, the brake booster uses the negative pressure in the intake pipe or there is a possibility of the brake booster using the negative pressure.
According to the warm-up control apparatus and the warm-up control method in the fifth aspect, if the brake booster uses the negative pressure or there is a possibility of the brake booster using the negative pressure, for example, if a brake operation or the like occurs, the amount of intake air increased by the warm-up control is reduced, so that the intake pipe negative pressure will be well recovered and good braking performance will be secured.